Ions are used in a plurality of semiconductor processes, such as implantation, amorphization, deposition and etching processes. These ions may be created within an ion source chamber and extracted through an extraction aperture in the ion source chamber.
The ions may be attracted through the extraction aperture by an optics system disposed outside and proximate the ion source chamber. Typical optic elements for an ion source include an extraction electrode, which may be the wall of the ion source chamber that includes the extraction aperture. Other optic elements include a suppression electrode and a ground electrode. The suppression electrode may be electrically biased to attract the ions created within the ion source chamber. For example, the suppression electrode may be negatively biased to attract positive ions from within the ion source chamber. In certain embodiments, there could be up to five electrodes with the addition of a focusing lens and an additional ground electrode.
The electrodes may each be a single electrically conductive component with an aperture disposed therein. Alternatively, each electrode may be comprised of two components that are spaced apart so as to create an aperture between the two components. In both embodiments, the ion beam passes through the aperture in each electrode. The portion of the electrode disposed proximate the aperture may be referred to as the optical edge. The portion of the electrode furthest from the aperture may be referred to as the distal edge.
It is not uncommon for some portion of the ion beam extracted from the ion source chamber to strike the suppression electrode, causing it to heat up along the optical edge. However, not all portions of the suppression electrode are equally impacted by the extracted ions. Consequently, the suppression electrode may be heated unevenly by these extracted ions.
In certain embodiments, the uneven heating of the suppression electrode may be problematic. This problem may be exacerbated as the length of the suppression electrode increases. Therefore, it would be beneficial if there were an apparatus and method to compensate or control the thermal distortion caused by this uneven heating.